Analyzing device

ABSTRACT

The present invention relates to an analyzing device ( 1 ) used with an analytical tool ( 2 ) mounted to the device, where the analytical tool provides a reaction field including sample liquid and includes a first and a second electrodes ( 20 A,  20 B) for applying voltage to the reaction field. The analyzing device ( 1 ) includes a connector ( 10 ) coming into contact with the first and the second electrodes ( 20 A,  20 B), an analysis circuit ( 13 ) for performing sample analysis based on sample liquid information obtained from the analytical tool ( 2 ) through the connector ( 10 ), and a disturbing-noise countermeasure unit ( 11 ) which absorbs disturbing noise and which is provided closer to the connector ( 10 ) than to the analysis circuit ( 13 ).

TECHNICAL FIELD

The present invention relates to a device for analyzing a particularcomponent in a sample liquid.

BACKGROUND ART

In a typical method for measuring a blood glucose level, redox reactionis utilized. Meanwhile, portable handheld blood glucose level measuringapparatuses are widely used so that the blood glucose level can beeasily measured at home or away from home. In such a portable bloodglucose level measuring apparatus, the blood glucose level is measuredby mounting a disposable biosensor for providing an enzymatic reactionfield to the apparatus and supplying blood to the biosensor.

The measurement of a blood glucose level may be performed by utilizingan electrochemical technique. In such a case, the biosensor as shown inFIG. 7 may be used which comprises an insulating substrate 80, and afirst and a second electrodes 81 and 82 for applying voltage to theenzymatic reaction field. The blood glucose level measuring apparatus 9comprises a connector 90 including a first and a second terminals 91 and92 for coming into contact with the first and the second electrodes 81and 82, and a measurement circuit 93 for determining the blood glucoselevel based on the information from the connector 90. (See JP-B 8-10208,for example.)

The blood glucose level measuring apparatus 9 is influenced by variousdisturbing noise. The disturbing noise may influence measurement resultsor destroy the electronic part to make the measurement impossible.Particularly, a portable small measurement apparatus is liable to staticelectricity from a human body. Generally, the biosensor 8 is manuallymounted to the blood glucose level measuring apparatus 9 shown in FIG.7. Therefore, the static electricity, if built up in the human body, isdischarged to the first and the second electrodes 81 and 82 of thebiosensor 8 or the first and the second terminals 91 and 92 of the bloodglucose level measuring apparatus 9. If no countermeasure is takenagainst such static electricity, the static electricity is inputted, asdisturbing noise, into the analysis circuit through the first electrode81, for example. Therefore, as the conventional measures to reduce theinfluence of static electricity, the arrangement of the first and thesecond electrodes 81, 82 of the biosensor 8 and the first and the secondterminals 91, 92 of the blood glucose level measuring apparatus 9 hasbeen contrived, or the withstand voltage of each electronic partconstituting the measurement circuit 93 has been increased.

Recently, there is a tendency to reduce the thickness of the first andthe second electrodes 81 and 82 to reduce the manufacturing cost of thebiosensor 8. Further, to adapt the biosensor 8 to the portable bloodglucose level measuring apparatus 9, the size of the biosensor 8,including the size of the first and the second electrodes 81 and 82,should be reduced. In such cases, the resistance of the first and thesecond electrodes 81 and 82 increases. Therefore, in the circuitstructure shown in FIG. 7, for example, Joule heat is generated near thecontact point between the first electrode 81 and the first terminal 91of the blood glucose level measuring apparatus 9 when static electricityflows through the contact point. When the generated Joule heat is high,the first electrode 81 may melt. In this case, the biosensor 8 mountedto the apparatus cannot measure the blood glucose level. Further, meltof the first electrode 81 of the biosensor 8 adheres to the firstterminal 91 of the blood glucose level measuring apparatus 9, therebychanging the effective resistance of the first terminal. Unfavorably,this leads to an error in the subsequent measurement of responsecurrent. Such a problem becomes more significant as the thickness of thefirst electrode 81 is made smaller.

DISCLOSURE OF THE INVENTION

An object of the present invention is to reduce the influence ofdisturbing noise, specifically, to make it possible to cope with staticelectricity even when the resistance of an electrode of an analyticaltool is relatively high.

According to the present invention, there is provided an analyzingdevice used with an analytical tool mounted to the device, where theanalytical tool provides a reaction field including sample liquid andincludes a first and a second electrodes for applying voltage to thereaction field. The analyzing device comprises a connector for cominginto contact with the first and the second electrodes, and an analysiscircuit for performing sample analysis based on sample liquidinformation obtained from the analytical tool through the connector. Theapparatus further includes a disturbing-noise countermeasure unit forabsorbing disturbing noise inputted through the connector.

In the analyzing device, the connector and the analysis circuit areconnected to each other by a signal line, for example. Thedisturbing-noise countermeasure unit may be provided at an inner pointof the signal line or at the connector. The disturbing-noisecountermeasure unit may include a resistor, a capacitor, a coil, aferrite core or a varistor. The disturbing-noise countermeasure unit maycomprise a combination of two or more components exemplified above.

As the analytical tool, use may be made of one that is adapted to causereaction of glucose in blood. Preferably, in this case, the analysiscircuit calculates the glucose level in blood based on the currentobtained when voltage is applied to the reaction field by utilizing thefirst and the second electrodes.

The concept of the present invention to provide a disturbing-noisecountermeasure unit is particularly effective for a portable analyzingdevice. To make an analyzing device portable, the dimension of theanalyzing device may be no more than 400 mm×300 mm×300 mm, and theweight of the apparatus may be no more than 2 kg. In this case, to storethe analyzing device in a bag or a pocket, it is preferable that thedimension of the apparatus is no more 150 mm×100 mm×500 mm and theweight is no more than 500g, and more preferably, the dimension is nomore than 100 mm×60 mm×15 mm and the weight is no more than 70g.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a perspective view showing an analyzing device according to thepresent invention, with a biosensor mounted thereto.

FIG. 2 is a sectional view taken along lines II-II in FIG. 1.

FIG. 3 schematically illustrates the state shown in FIG. 1, with theanalyzing device represented in circuit block diagram and with thebiosensor represented in plan view.

FIG. 4 is a circuit diagram showing examples of circuit of thedisturbing-noise countermeasure unit.

FIG. 5 is an exploded perspective view of the biosensor.

FIG. 6 is a schematic view corresponding to FIG. 3, showing anotherexample of analyzing device.

FIG. 7 is a schematic view for describing a conventional portable bloodglucose level measuring device and a biosensor.

BEST MODE FOR CARRYING OUT THE INVENTION

The analyzing device 1 shown in FIGS. 1 through 3 is of a portable type,to which a biosensor 2 is mounted in use. The analyzing device 1includes a connector 10, a disturbing-noise countermeasure unit 11, acurrent/voltage conversion amplifier 12, an analysis circuit 13, aplurality of operation buttons 14 and a display 15.

The connector 10, utilized for inserting an end 2 a of the biosensor 2,includes a first and a second terminals 10 a and 10 b. The first and thesecond terminals 10 a and 10 b, utilized for applying voltage to atarget portion of the biosensor 2, is made springy to press the end 2 aof the biosensor 2, as shown in FIG. 2. The connector 10 is electricallyconnected to the analysis circuit 13 via a signal line 16. Thedisturbing-noise countermeasure unit 11 and the current/voltageconversion amplifier 12 are arranged on the signal line 16.

The disturbing-noise countermeasure unit 11 shown in FIG. 3 copes withstatic electricity coming from a human body, for example, and includesat least one of a resistor, a capacitor, a coil, a ferrite core and avaristor.

FIGS. 4A-4G show examples of circuit of the disturbing-noisecountermeasure unit 11. In the example of circuit shown in FIG. 4A, thedisturbing-noise countermeasure unit 11 includes a capacitor C. In theexample of circuit shown in FIG. 4B, the disturbing-noise countermeasureunit 11 includes a resistor R. In the example of circuit shown in FIG.4C, the disturbing-noise countermeasure unit 11 includes a coil L. Inthe example of circuit shown in FIG. 4D, the disturbing-noisecountermeasure unit 11 includes a resistor R, and a capacitor C disposedon a line connected to ground downstream of the resistor R. In theexample of circuit shown in FIG. 4E, the disturbing-noise countermeasureunit 11 includes a coil L, and a capacitor C₁ and C₂ respectivelydisposed upstream and downstream of the coil L on lines connected toground. In the example of circuit shown in FIG. 4F, the disturbing-noisecountermeasure unit 11 includes a resistor R and a capacitor C arrangedin parallel. In the example of circuit shown in FIG. 4G, thedisturbing-noise countermeasure unit 11 includes two coils L₁ and L₂,and a capacitor C disposed between the coils L₁ and L₂ on a lineconnected to ground.

The circuit structure of the disturbing-noise countermeasure unit 11 isnot limited to those described above. Further, the parts of thedisturbing-noise countermeasure unit are not limited to thoseexemplified above. The disturbing-noise countermeasure unit may compriseother parts which are capable of removing or reducing disturbing noise.

The current/voltage conversion amplifier 12 shown in FIG. 3 converts theinformation obtained, as a current, from the biosensor 2 into a voltageto be inputting into the analysis circuit 13.

For example, based on the information outputted from the current/voltageconversion amplifier 12, the analysis circuit 13 calculates theconcentration of a particular component in a sample liquid or determineswhether or not the content of a particular component in the sampleliquid is not less than a predetermined level. The analysis circuit 13,having functions equivalent to those of a so-called microprocessor, iscomposed of a CPU for controlling operations such as calculation, a ROMfor storing an operation program for e.g. calculation, a RAM for storinginformation required for operation, and so forth.

The operation buttons 14 are used for inputting various kinds ofinformation into the analyzing device 1. For example, the buttons areused for sending analysis start instruction or for setting the analyzingdevice 1.

The display 15 may comprise a liquid crystal display unit, for example,for displaying e.g. analysis results, procedure instructions, and errormessages.

As shown in FIGS. 2, 3 and 5, the biosensor 2 includes a substrate 20, acover 22 stacked on the substrate via a spacer 21, and a flow path 23defined by the parts 20-22. In the flow path 23, a reaction field isprovided, and the sample liquid introduced via a sample liquidintroduction port 23 a is caused to flow toward a hole 22 a of the cover22 by capillary action. The size of the flow path 23 is determined by aslit 21 a formed in the spacer 21.

The substrate 20 is provided with a working electrode 20A and a counterelectrode 20B for applying voltage to the reaction field. The ends 20Aaand 20Ba of the working electrode 20A and the counter electrode 20B areconnected to each other by a reagent portion 24. As better shown inFIGS. 2 and 3, when the biosensor 2 is mounted to the connector 10 ofthe analyzing device 1, the ends 20Ab and 20Bb of the working electrode20A and the counter electrode 20B are brought into contact with thefirst and the second terminals 10 a and 10 b of the analyzing device 1.The reagent portion 24 is in a solid state containing an oxidoreductaseand an electron mediator, for example, and dissolves when a sampleliquid is supplied thereto. The kinds of oxidoreductase and electronmediator are selected depending on the kind of the component to bemeasured, for example. For example, in the case of measuring a glucoselevel, glucose dehydrogenase or glucose oxidase is used as theoxidoreductase, and potassium ferricyanide is used as the electronmediator.

To perform the analysis of a sample liquid by the analyzing device 1,after the biosensor 2 is mounted to the analyzing device 1, the sampleliquid (typically blood or urine) is introduced through the sampleintroduction port 23 a of the biosensor 2. In the biosensor 2, thesample liquid moves within the flow path 23 by capillary action andfills the flow path 23. The sample liquid dissolves the reagent portion24 to produce a liquid phase reaction system in the flow path 23. Then,voltage is applied to the liquid phase reaction system by e.g. a DCpower source (not shown) of the analyzing device 1. The response currentobtained is inputted into the current/voltage conversion amplifier 12through the working electrode 20A of the biosensor 2, the first terminal10 a of the analyzing device 1 and the disturbing-noise countermeasureunit 11. The information converted from current into voltage at thecurrent/voltage conversion amplifier 12 is then converted into a digitalsignal by a non-illustrated A/D converter and inputted into the analysiscircuit 13. Based on the digital signal corresponding to the responsecurrent, the analysis circuit 13 performs analysis of the sample liquidsuch as determination of the glucose level in blood. The analysis resultis displayed at the display 15 of the analyzing device 1, for example.

In mounting the biosensor 2 to the analyzing device 1, as noted above,static electricity built up in a human body may be discharged to theworking electrode 20A and the counter electrode 20B of the biosensor 2,or the first and the second terminals 10 a, 10 b of the analyzing device1. In the analyzing device 1, the disturbing-noise countermeasure unit11 copes with such static electricity. Specifically, when staticelectricity comes from the outside of the analyzing device 1, thedisturbing-noise countermeasure unit 11 consumes or stores the staticelectricity. Therefore, it is possible to reduce the consumption ofstatic electricity, i.e. the generation of Joule heat adjacent to thecontact point between the first terminal 10 a of the analyzing device 1and the working electrode 20A of the biosensor 2, so that the end 20Abof the working electrode 20A is prevented from melting. Moreover, byabsorbing static electricity by the disturbing-noise countermeasureelectrode 11, the input of static electricity into the analysis circuit13 as noise can be prevented. Therefore, in the analyzing device 1,measurement failure and measurement error due to static electricity canbe prevented. The disturbing-noise countermeasure unit 11 absorbs notonly the static electricity coming from a human body but also otherdisturbing noise. Particularly, since the disturbing-noisecountermeasure unit 11 of the analyzing device 1 is provided closer tothe connector 10 than to the analysis circuit 13, the disturbing noiseinputted through the connector 10 is reliably prevented from beinginputted into the analysis circuit 13.

In the above embodiment, the disturbing-noise countermeasure unit 11 isprovided at an inner point of the signal line 16 that connects theanalysis circuit 13 and the connector 10 to each other. However, asshown in FIG. 6, the disturbing-noise countermeasure unit 11 may beprovided at the connector 10.

1. An analyzing device used with an analytical tool mounted to thedevice, the analytical tool providing a reaction field that includessample liquid and comprising a first and a second electrodes forapplying voltage to the reaction field, the analyzing device comprising:a connector coming into contact with the first and the secondelectrodes; and an analysis circuit for performing sample analysis basedon sample liquid information obtained from the analytical tool throughthe connector; wherein the analyzing device comprises a disturbing-noisecountermeasure unit for absorbing disturbing noise inputted through theconnector.
 2. The analyzing device according to claim 1, furthercomprising a signal line connecting the connector and the analysiscircuit to each other; wherein the disturbing-noise countermeasure unitis provided at an inner point of the signal line.
 3. The analyzingdevice according to claim 1, wherein the disturbing-noise countermeasureunit is provided at the connector.
 4. The analyzing device according toclaim 1, wherein the disturbing-noise countermeasure unit comprises aresistor.
 5. The analyzing device according to claim 1, wherein thedisturbing-noise countermeasure unit comprises a capacitor.
 6. Theanalyzing device according to claim 1, wherein the disturbing-noisecountermeasure unit comprises a coil.
 7. The analyzing device accordingto claim 1, wherein the disturbing-noise countermeasure unit comprises aferrite core.
 8. The analyzing device according to claim 1, wherein thedisturbing-noise countermeasure unit comprises a varistor.
 9. Theanalyzing device according to claim 1, wherein the disturbing-noisecountermeasure unit comprises a combination of at least two selectedfrom the group consisting of a resistor, a capacitor, a coil, a ferritecore and a varistor.
 10. The analyzing device according to claim 9,wherein the disturbing-noise countermeasure unit comprises a combinationof at least two selected from the group consisting of the resistor, thecapacitor and the coil.
 11. The analyzing device according to claim 1,wherein the analytical tool is adapted to measure a glucose level inblood; and wherein the analysis circuit calculates the glucose level inblood based on a current obtained when voltage is applied to thereaction field by utilizing the first and the second electrodes.
 12. Theanalyzing device according to claim 11, wherein the analytical toolcomprises a reagent portion containing a reagent to react with glucose.13. The analyzing device according to claim 1, wherein the device isportable.